1. Field of the Invention
The invention is particularly related to the art of centrifugal compressors as used in gas turbine engines. More particularly, the invention is concerned with an improved treatment for the casing in the inducer-diffuser section of a centrifugal compressor which leads to a reduction in surge flow and hence to a reduction in the flow value at which stalling of the inducer section of the compressor occurs.
2. Prior Art
The prior art teaches centrifugal compressors which include an inducer section including an impeller having a plurality of impeller blades rotatingly driven by a shaft of the compressor to impel air centrifugally outwardly from the shaft with an air intake duct defined in a casing radially about the impeller blades and a diffuser with a plurality of diffuser vanes in the duct downstream a spaced vane-free distance from a downstream end of the impeller. The prior art does not teach providing any slots, grooves, or the like in the casing of a centrifugal compressor to in any way affect surge flow and thereby the minimum flow value at which stalling of the inducer section of the compressor occurs. Some use has been made of internal grooving and/or other types of slots in axial compressors but the flow paths therein are so different than the flow paths within centrifugal compressors that it was not previously believed that such treatment could affect centrifugal compressors in an advantageous manner.